As it is known by the technicians skilled in the art, hermetic reciprocating compressors comprise equipment capable to compress a certain work fluid. Normally applied in refrigeration systems, the hermetic reciprocating compressors are, therefore, capable of compressing any refrigerating fluid.
In general, hermetic reciprocating compressors are composed by a compression unit enclosed in a hermetic housing.
The compression unit comprises all the functional set of the compressor, that is, the compressor block, the array head-cylinder-piston and the compressor engine. A hermetic housing, as defined by nomenclature itself comprises a receptacle, its inside volume free from hard contact with the inside environment, able to house inside it the referred compression unit.
Conventionally, and as it is known to the technicians skilled in the art, the compression unit is enclosed in the hermetic housing in a semi flexible way, that is, through suspension systems and especially pipes that allow, up to a certain point, the mobility of the compression unit inside the hermetic housing.
Moreover, the state of the art comprises a vast variety of models and variations of suspension systems used to support the mobile unit inside the hermetic housing of the hermetic reciprocating compressor.
The prior art document U.S. Pat. No. 4,174,189 discloses a suspension system including a shipping stop arrangement for resiliently mounting a refrigeration motor-compressor unit within a hermetically sealed shell
The document US2005201875 discloses a linear compressor having a dynamic vibration-reducing unit, which is provided at a stopper, by which separation of a cylinder block is prevented, for eliminating vibration generated from a hermetically sealed container at a specific frequency band.
Another embodiment may be seen at document GB923759, wherein a resilient support of an electric motor compressor unit mounted vertically within an hermetically sealed outer casing, said motor been affected firstly by a coil spring extending between the bottom of casing and a recess.
Finally the document GB875547 discloses a hermetically sealed compressor comprising a motor-compressor unit resiliently mounted within a casing, and the weight of the unit is normally taken by a spring mounted within a ringed cup and located with respect to the unit by a pin welded thereon.
The current models of suspension systems used to support a mobile unit inside the hermetic housing of a hermetic reciprocating compressor allow, therefore, that the mobile unit eventually contacts the internal face of the hermetic housing.
This happens mainly with hermetic reciprocating compressor for mobile applications such as, for example, with hermetic reciprocating compressors used in refrigeration systems of automotive vehicles. This is because the movement of the automotive vehicle applies dynamic forces on the compression unit, which tends to move inside the hermetic housing.
As it has already been mentioned, it cam be considered as common the occurrence of shocks between the compression unit and the inside wall of the hermetic housing. Such shocks, depending on its intensity may in the end damage and undermine certain components of the compression unit. This characteristic, by itself alone, is extremely negative.
Aiming at the solution of this problem, one can observe the existence of certain sets to limit the movement of the compression unit.
DE102007052580 describes, for example, a movement limiting set constituted essentially of an end stop attached to the inside upper portion of the hermetic housing and a body to house the end stop attached to the compression unit.
More specifically, DE102007052580 describer that the body for the end stop housing is attached to the compression unit through screws that attach the cover of the head to the compressor block and comprises a perforated region (or opening) to house the end stop of the housing.
Since the perforated region has dimensions that are greater than the dimensions of the end stop, there can be observed a kind of mechanical gap between them. Therefore, the free movement of the compression unit, inside the hermetic housing, is reduced to the mechanical gap existing between the perforated region of the body of the housing and the end stop of the hermetic housing.
Therefore, the movements of the compression unit, if they are greater that the mechanical gap between the perforated region of the hermetic housing and the end stop of the hermetic housing, they are limited by the physical contact between the end stop of the hermetic housing and the housing body of the compression unit.
Though it is theoretically interesting, the movement limiting set described in DE102007052580 presents, two great drawbacks.
The first drawback is related to the rattling and/or noises generated by the physical contact between the end stop of the hermetic housing and the housing body of the compression unit. Since both the components are hard (and usually metallic), each contact between them generates an undesirable noise its amplitude varying depending on the energy of the physical contact. Thus, the stronger the physical contact between the end stop of the hermetic housing and the housing body of the compression unit, the greater is the amplitude of the rattling and/or noise.
This negative aspect is increased in hermetic reciprocating compressors for mobile application, where the movement of the compression unit inside the hermetic housing is predominantly greater and stronger.
The second negative aspect is the range of movement limitation that the movement limiting set described in DE102007052580 is capable of providing to the compression unit.
As it is possible to verify, the movement limiting set mentioned described in DE102007052580 is capable to work in only one dimensional direction of the movement of the compression unit, that is, only in the horizontal direction of the compression unit.
Consequently, any vertical movement of the compression unit inside the hermetic housing is not limited by the movement limiting set. Thus, only part of the three-dimensional movements of the compression unit is limited and there is no way of preventing the contact (shock) of the compression unit with the other portions of the hermetic housing.
This negative aspect is also increased in hermetic reciprocating compressors for mobile application where the movement of the compression unit inside the hermetic housing is predominantly three-dimensional.
With the solution of these negative aspects in view, the current state of the art further comprises the movement limiting set described in CN101871445.
As it happens with the movement limiting set described in DE102007052580, the movement limiting set described in CN101871445 is essentially aimed at hermetic reciprocating compressors and is essentially composed by an end stop attached to the inside upper portion of the hermetic housing, and a housing body of the end stop attached to the compression unit. There is further provided a connection spring between the referred end stop and the said housing body of the end stop.
Moreover, there is further mentioned that the perforated region of the housing body of the end stop intended to house the end stop of the housing may accept a damping ring made from a resilient material (using, preferably, a polymeric alloy).
Thus, the movement limiting set described in CN101871445 is, theoretically, able to reduce the two great negative aspects existing in the movement limiting set described in DE102007052580.
This happens because the damping ring is, theoretically, able do reduce the rattling and or noises arising from the physical contact between the end stop of the hermetic housing and the housing body of the compression unit.
Moreover, the spring connecting the end stop and the housing body of the end stop is also, theoretically, able to restrict and or limit the vertical movements the compression unit may perform inside the hermetic housing, preventing, at the same time, the end stop from displacing the housing body.
However, the movement limiting set described in CN101871445 has its own negative aspects.
As it can be observed, the addition of a connection spring means, just by itself, a negative aspect from the economical and technical point of view.
From the economical point of view, the addition of a connection spring means manufacturing and mounting of an additional component, said manufacturing and mounting involving additional costs capable of raising the costs of the making of the compressor. Furthermore, the addition of this additional component, however small, increases the total weight of the compressor, which may increase the costs of the transportation.
From the technical point of view, employing the connection spring as an element for the limitation of the vertical movement of the compression unit, in relation to the hermetic housing, is only effective in the short run, for the extended use of the said spring, mainly in mobile applications, reduces its resilient elastic characteristic, resulting in the reduction of its performance.
Therefore, with the view of solving of problems related to the movement limiting set described in DE102007052580, in a different way from the solution described in CN101871445, there arose the present invention.